package com.wuliang.generate.api.filters;

import com.wuliang.generate.common.core.utils.JsonUtils;
import org.reactivestreams.Publisher;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferFactory;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.io.buffer.DefaultDataBufferFactory;
import org.springframework.http.server.reactive.ServerHttpResponse;
import org.springframework.http.server.reactive.ServerHttpResponseDecorator;
import org.springframework.stereotype.Component;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.nio.charset.StandardCharsets;

/**
 * @author WuLiang
 */
@Component
public class WrapperResponseGlobalFilter implements GlobalFilter, Ordered {

    @Override
    public int getOrder() {
        // -1 is response write filter, must be called before that
        return -2;
    }

    @Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        ServerHttpResponse originalResponse = exchange.getResponse();
        DataBufferFactory bufferFactory = originalResponse.bufferFactory();
        ServerHttpResponseDecorator decoratedResponse = new ServerHttpResponseDecorator(originalResponse) {
            @Override
            public Mono<Void> writeWith(Publisher<? extends DataBuffer> body) {
                if (body instanceof Flux) {
                    Flux<? extends DataBuffer> fluxBody = (Flux<? extends DataBuffer>) body;

                    return super.writeWith(fluxBody.buffer().map(dataBuffers -> {

                        DataBufferFactory dataBufferFactory = new DefaultDataBufferFactory();
                        DataBuffer join = dataBufferFactory.join(dataBuffers);

                        byte[] content = new byte[join.readableByteCount()];

                        join.read(content);
                        // 释放掉内存
                        DataBufferUtils.release(join);
                        String str = new String(content, StandardCharsets.UTF_8);
                        str = JsonUtils.toJson(JsonUtils.jsonToMap(str));
                        originalResponse.getHeaders().setContentLength(str.getBytes().length);
                        return bufferFactory.wrap(str.getBytes());
                    }));

                }
                // if body is not a flux. never got there.
                return super.writeWith(body);
            }
        };
        // replace response with decorator
        return chain.filter(exchange.mutate().response(decoratedResponse).build());
    }

}
